Curved Roof Planes

Any roof plane can be turned into a curved roof plane in the Roof Plane Specification dialog. See "Roof Plane Specification Dialog".

One way to produce a barrel roof is using a single roof plane that starts out flat (zero pitch) and covers the entire building.

Curving a Single Roof Plane

To curve a roof plane

Draw a simple four wall structure 18' x 24', set three of the walls as High/Shed Gable walls on the Roof tab of the Wall Specification dialog and automatically generate a roof. The initial pitch does not matter. Tiling the floor plan view and a cross section/elevation view may be helpful.

Select the roof plane in floor plan view and click the Open Object

edit button to open the Roof Plane Specification dialog for that roof plane.

Change the Pitch from 4 in 12 to 0 in 12 to flatten the roof.

On the General tab, check Curved Roof. Notice that the angle values are currently at zero.

Change the Angle at eave from zero to 15 and press the Tab key. Notice that the other values update. All three values are interrelated and dynamic. Changing one changes the others. In order to maintain the underlying 0 in 12 pitch (the chord of the curved roof), the other end of the roof plane must compensate.

Change the Angle at Ridge from -15 degrees to -45 degrees.

Change the Radius to roof surface to a smaller number, such as 50.

A radius of 50 could not be achieved unless the walls were closer together. The curved roof plane accepts the minimum radius, which is 116.5.

Curving Two Roof Planes

You can also create a barrel roof using two roof planes. We'll use the same basic 24' x 18' plan we used before, designate the two opposite walls as gable walls, and generate a gable with a 12 in 12 (45 degree) pitch. The 12 in 12 pitch often underlies curved roofs because it allows the curved roof to be nearly vertical at the eave and nearly flat at its peak.

To curve two roof planes

Draw a simple four wall structure 18' x 24', set the two end walls as Gable Walls, and automatically generate a roof at a 12 in 12 pitch.

Select one of the roof planes in floor plan view and click the Open Object

edit button to open the Roof Plane Specification dialog for that roof plane.

Check Curved Roof and notice that the values are the same. Change the Angle at ridge from 45 to 0. This makes the roof plane nearly flat at the ridge. The eave edge has to compensate to maintain the 12 in 12 pitch.

Notice that the program changed the Angle at Ridge from 0 to 1 so that the eave does not become vertical at 90°. Curved roofs are not allowed to be vertical or inverted.

In floor plan view, select both roof planes and click the Open Object

edit button to open the Roof Plane Specification dialog.

Set the Angle at ridge to 0 and click OK.

Similar results can be achieved using two roof planes instead of one. Because the curvature can be set independently for each roof plane, using two roof planes allows more variation.

Compound Curved Roof Planes

Compound roof planes consisting of two or more roof planes that merge together can be defined using curved roofs. To illustrate this, we'll produce a flared "Thai" style roof eave that is almost flat at the eave edge and merges into an 8 in 12 pitch roof.

To create a compound curved roof

Draw a simple four wall structure 18' x 24', set the two end walls as Gable Walls, and automatically generate a roof at a 4 in 12 pitch.

Turn on Display Temporary Dimensions

, select one of the roof planes in floor plan view at its ridge edge and pull it back so that it is 4 feet from the wall. Do the same to the other roof plane.

Select both roof planes in floor plan view and check Curved Roof in the Roof Plane Specification dialog. Set the Angle at Ridge to 33.6901, which is the same as 8 in 12. Notice that the Angle at Eave is almost flat.

To create the high roof plane, use the Roof Plane

tool and draw the baseline of the roof plane along the top, or ridge edge of the curved roof plane in floor plan view. The bottom edge of the new roof plane snaps to the top of the curved plane.

Select the two new roof planes, open them for specification and change their pitch to 33.6901. Viewed in 3D, the planes appear to join together into one.